Preparation method of styrene thermoplastic elastomer

Abstract

The invention discloses a styrene thermoplastic elastomer preparation method, which comprises: uniformly mixing a styrene monomer, a solvent cyclohexane and an activator tetrahydrofuran, heating to a temperature of 45-55 DEG C, adding an initiator n-butyllithium, and carrying out a reaction for 20-30 min under a stirring state; adding an isoprene monomer or a butadiene monomer when the temperature is 55-60 DEG C, controlling the reaction temperature to be lower than 105 DEG C, and reacting for 20-30 minutes; adding a coupling agent, and continuously reacting for 5-25 minutes in a stirring state; and discharging, and carrying out post-treatment on the glue solution to obtain the styrene thermoplastic elastomer. The coupling agent is one or a mixture of more of methyl benzoate, ethyl benzoate and ethyl acetate. The preparation method has the advantages that the use temperature of the prepared thermoplastic elastomer can be adjusted in a small range, so that the fracture rate of a coupling bond can be controlled, and the thermoplastic elastomer with the required SI content can be generated.

Description

Technical Field

[0001] The invention relates to the technical field of thermoplastic elastomers, in particular to a method for preparing a styrene-based thermoplastic elastomer. Background Art

[0002] Styrene thermoplastic elastomers (such as SIS, SBS, SIBS, etc.) can be plasticized and formed at high temperatures, and show rubber elasticity characteristics at room temperature. They are usually synthesized by anionic polymerization. There are currently three main synthesis methods: the first is the sequential monomer polymerization method, that is, in an alkane medium, using organic lithium as an initiator, first polymerizing styrene monomers, adding conjugated diene monomers after the polymerization is completed, and finally adding the remaining styrene monomers for copolymerization. After the polymerization is completed, an antioxidant is added, and the final product is obtained after the glue is desolvated and dried. The product has a linear structure and is represented by SDS, where S represents the styrene monomer segment and D represents the conjugated diene monomer segment. This method is currently the most common synthesis method in the industry. The second is the coupling method. The first two steps of the feeding method are the same as the sequential monomer polymerization method, except that in the third step, nucleophilic compounds (usually bifunctional halogenated silanes, such as dichlorodimethylsilane) are added to couple with the anionic active species in the system. Due to the steric hindrance effect, the coupling efficiency cannot reach 100%, so the final product is a mixture of SDS and SD, but the coupling method successfully avoids the third step of the slowest cross-reaction in the sequential monomer polymerization method, thereby improving production efficiency. For example, in patent application CN112812250A, dichlorodimethylsilane is selected as a coupling agent, and a series of styrene thermoplastic elastomers are prepared by the coupling method. The third synthesis method is the star branching method, which has the same principle as the coupling method, except that the functionality of the nucleophilic compound is ≥3 (such as silicon tetrachloride), so the final product is a mixture of (SD)n and SD. For example, in patent application CN108395511A, silicon tetrachloride is selected as a coupling agent, and a series of styrene thermoplastic elastomers are prepared by the star branching method.

[0003] In order to improve the physical properties and application performance of the product, a certain amount of diblock polymer (SD) will be artificially controlled in the product during the production process. Taking SIS as an example, the molecular structure of the diblock SI is defective and does not have physical cross-linking. Although it will reduce the physical and mechanical strength of the product, it will improve the fluidity of the product and the wettability of the hot melt pressure-sensitive adhesive. In order to meet different application requirements, elastomer manufacturers will produce grades with different SI contents. Taking SIS as an example, the SI content can range from 0 to 80%, and a certain SI content range (every 5%) corresponds to a grade. In order to produce different grades of elastomers, the production parameters need to be adjusted accordingly, which will not only affect the stable production of the manufacturer; downstream manufacturers also have to purchase different grades of elastomers to meet production needs, which greatly increases the reserve cost of raw materials.

[0004] Existing styrene thermoplastic elastomers mainly use chlorosilane compounds as coupling agents, such as dichlorodimethylsilane. Styrene thermoplastic elastomer manufacturers need to control the SI content in the elastomer by adjusting the amount of coupling agent added. The elastomer products produced by the manufacturers have high bond energy after the coupling reaction of the chlorosilane coupling agent within the downstream use temperature range (about 100°C-200°C). Under the downstream use temperature conditions, the coupling bond will not break, and the SI content in the elastomer will not change with the change of the use temperature. Downstream manufacturers can only purchase elastomers of different brands. Summary of the invention

[0005] The purpose of the present invention is to make up for the above-mentioned deficiencies and disclose to the public a method for preparing a styrene-based thermoplastic elastomer. The prepared thermoplastic elastomer can control the breaking rate of the coupling bonds by adjusting the use temperature within a small range to generate a thermoplastic elastomer with a desired SI content.

[0006] The technical solution of the present invention is achieved in this way: A method for preparing a styrene-based thermoplastic elastomer comprises the following steps: Step 1: Add styrene monomer, solvent cyclohexane and activator tetrahydrofuran into a reaction kettle, mix well and heat to 45°C to 55°C, add initiator n-butyl lithium, react under stirring for 20min to 30min; Step 2: adding isoprene monomer or butadiene monomer at a temperature of 55°C to 60°C, controlling the reaction temperature to be lower than 105°C, and reacting for 20min to 30min; Step 3, adding a coupling agent, and continuing the reaction for 5 to 25 minutes under stirring; discharging the material, and post-treating the glue to obtain a styrene-based thermoplastic elastomer product; the coupling agent is one of methyl benzoate, ethyl benzoate, and ethyl acetate, or a mixture of several thereof; The mass ratio of styrene monomer to isoprene monomer or butadiene monomer is 1:9 to 1:1; The molar ratio of coupling agent to initiator is 0.05~0.5.

[0007] The measures to further optimize this technical solution are: Furthermore, the styrene monomer is styrene or α-methylstyrene.

[0008] Furthermore, in the step three, after discharging, antioxidants BHT and TNP are added to the glue solution, and the amounts of antioxidants BHT and TNP are both 0.3wt% to 0.6wt% of the total amount of styrene monomers. The mixture is stirred evenly, and the glue solution is condensed and dried to obtain a styrene thermoplastic elastomer product.

[0009] Furthermore, the melt index of the styrene-based thermoplastic elastomer product is 0.1 to 30.0.

[0010] Furthermore, the molecular weight of the styrene-based thermoplastic elastomer product is 50,000 to 400,000.

[0011] Furthermore, in step three, after discharging, the solid content of the glue solution is 12wt% to 18wt%.

[0012] The advantages of the present invention compared with the prior art are: The preparation method of the present invention adopts one or a mixture of methyl benzoate, ethyl benzoate and ethyl acetate as a coupling agent to synthesize a styrene-based thermoplastic elastomer with heat-sensitive coupling points. After the coupling reaction occurs, the bond energy of the generated coupling bond is moderate, and within the downstream use temperature range (about 100° C.-200° C.), the coupling bond will be partially broken. The downstream manufacturer can control the breaking rate of the coupling bond by adjusting the use temperature within a small range to generate an elastomer with a required SI content. This is very convenient for elastomer manufacturers and downstream application manufacturers, and saves the trouble of the elastomer manufacturer adjusting the amount of coupling agent for producing different SI contents, and also greatly saves the elastomer preparation cost of the downstream application manufacturer. DETAILED DESCRIPTION

[0013] A method for preparing a styrene-based thermoplastic elastomer comprises the following steps: Step 1: Add styrene monomer, solvent cyclohexane and activator tetrahydrofuran into a reaction kettle, mix well and heat to 45°C to 55°C, add initiator n-butyl lithium, react under stirring for 20min to 30min; the styrene monomer is styrene or α-methylstyrene.

[0014] Step 2: adding isoprene monomer or butadiene monomer at a temperature of 55°C to 60°C, controlling the reaction temperature to be lower than 105°C, and reacting for 20min to 30min; Step 3, adding a coupling agent, and continuing the reaction under stirring for 5min to 25min; discharging, adding antioxidant BHT and antioxidant TNP to the glue solution, the amount of antioxidant BHT and antioxidant TNP is 0.3wt% to 0.6wt% of the total amount of styrene monomers, stirring evenly, and the glue solution is condensed and dried to obtain a styrene thermoplastic elastomer product; the coupling agent is one of methyl benzoate, ethyl benzoate, and ethyl acetate, or a mixture of several thereof; after discharging, the solid content of the glue solution is 12wt% to 18wt%; The mass ratio of styrene monomer to isoprene monomer or butadiene monomer is 1:9 to 1:1; The molar ratio of coupling agent to initiator is 0.05~0.5.

[0015] The melt index of the styrene-based thermoplastic elastomer product is 0.1 to 30.0.

[0016] The molecular weight of the styrene-based thermoplastic elastomer product is 50,000 to 400,000. Example

[0017] Add 2.5 kg of cyclohexane, 75 g of styrene and 0.3 g of tetrahydrofuran to a 5 L reactor, add 5 mmol of initiator n-butyl lithium at 45-55 ° C, and react for 25 minutes. Then add 425 g of isoprene, control the maximum temperature to be less than 105 ° C, and react for 25 minutes. Finally, add 2.3 mmol of methyl benzoate and react for 25 minutes. Discharge, add antioxidant BHT 2.0 g and TNP 2.5 g, stir evenly, and after condensation and drying, the SI content of the product is tested to be 10.0%.

[0018] SIS was subjected to heating test: at 100℃, 0.5h, the SI content was 11.0%; at 130℃, 0.5h, the SI content was 15.0%; at 150℃, 0.5h, the SI content was 30.0%; at 180℃, 0.5h, the SI content was 41.0%; at 200℃, 0.5h, the SI content was 51.0%. Example

[0019] Add 2.5 kg of cyclohexane, 75 g of styrene and 0.3 g of tetrahydrofuran to a 5L reactor, add 5 mmol of initiator n-butyl lithium at 45-55°C, and react for 25 minutes. Add 425 g of isoprene, control the maximum temperature to less than 105°C, and react for 25 minutes. Finally, add 2.3 mmol of ethyl benzoate and react for 25 minutes. Discharge, add antioxidant BHT 2.0 g and TNP 2.5 g, stir evenly, and after condensation and drying, the SI content of the product is tested to be 11.0%; SIS was subjected to heating test: at 100℃, 0.5h, the SI content was 11.0%; at 130℃, 0.5h, the SI content was 16.0%; at 150℃, 0.5h, the SI content was 32.0%; at 180℃, 0.5h, the SI content was 42.0%; at 200℃, 0.5h, the SI content was 50.0%. Example

[0020] Add 2.5 kg of cyclohexane, 75 g of styrene and 0.3 g of tetrahydrofuran to a 5 L reactor, add 5 mmol of initiator n-butyl lithium at 45-55 ° C, and react for 25 minutes. Then add 425 g of isoprene, control the maximum temperature to be less than 105 ° C, and react for 25 minutes. Finally, add 2.3 mmol of ethyl acetate and react for 25 minutes. Discharge, add antioxidant BHT 2.0 g and TNP 2.5 g, stir evenly, and after condensation and drying, the SI content of the product is tested to be 9.0%.

[0021] SIS was subjected to heating test: at 100℃, 0.5h, the SI content was 10.0%; at 130℃, 0.5h, the SI content was 14.0%; at 150℃, 0.5h, the SI content was 29.0%; at 180℃, 0.5h, the SI content was 41.0%; at 200℃, 0.5h, the SI content was 52.0%. Example

[0022] Add 2.5 kg of cyclohexane, 75 g of styrene and 0.3 g of tetrahydrofuran to a 5 L reactor, add 5 mmol of initiator n-butyl lithium at 45-55 ° C, and react for 25 minutes. Then add 425 g of isoprene, control the maximum temperature to be less than 105 ° C, and react for 25 minutes. Finally, add 1.2 mmol of methyl benzoate and 1.1 mmol of ethyl benzoate at the same time, and react for 25 minutes. Discharge, add antioxidant BHT 2.0 g and TNP 2.5 g, stir evenly, and after the product is condensed and dried, the SI content is tested to be 10.0%.

[0023] SIS was subjected to heating test: at 100℃, 0.5h, the SI content was 11.0%; at 130℃, 0.5h, the SI content was 16.0%; at 150℃, 0.5h, the SI content was 29.0%; at 180℃, 0.5h, the SI content was 43.0%; at 200℃, 0.5h, the SI content was 51.0%. Example

[0024] Add 2.5 kg of cyclohexane, 75 g of styrene and 0.3 g of tetrahydrofuran to a 5 L reactor, add 5 mmol of initiator n-butyl lithium at 45-55 ° C, and react for 25 minutes. Then add 425 g of isoprene, control the maximum temperature to be less than 105 ° C, and react for 25 minutes. Finally, add 1.1 mmol of ethyl benzoate and 1.2 mmol of ethyl acetate at the same time, and react for 25 minutes. Discharge, add 2.0 g of antioxidant BHT and 2.5 g of TNP, stir evenly, and after condensation and drying, the SI content of the product is tested to be 10.0%.

[0025] SIS was subjected to heating tests: at 100°C and 0.5h, the SI content was 11.0%; at 130°C and 0.5h, the SI content was 15.0%; at 150°C and 0.5h, the SI content was 28.0%; at 180°C and 0.5h, the SI content was 43.0%; and at 200°C and 0.5h, the SI content was 51.0%. Example

[0026] Add 2.5 kg of cyclohexane, 75 g of styrene and 0.3 g of tetrahydrofuran to a 5 L reactor, add 5 mmol of initiator n-butyl lithium at 45-55 ° C, and react for 25 minutes. Then add 425 g of isoprene, control the maximum temperature to be less than 105 ° C, and react for 25 minutes. Finally, add 1.2 mmol of methyl benzoate and 1.1 mmol of ethyl acetate at the same time, and react for 25 minutes. Discharge, add antioxidant BHT 2.0 g and TNP 2.5 g, stir evenly, and after the product is condensed and dried, the SI content is tested to be 10.0%.

[0027] SIS was subjected to heating test: at 100℃, 0.5h, the SI content was 10.0%; at 130℃, 0.5h, the SI content was 14.0%; at 150℃, 0.5h, the SI content was 28.0%; at 180℃, 0.5h, the SI content was 42.0%; at 200℃, 0.5h, the SI content was 52.0%. Example

[0028] Add 2.5 kg of cyclohexane, 75 g of styrene and 0.3 g of tetrahydrofuran to a 5 L reactor, add 5 mmol of initiator n-butyl lithium at 45-55 ° C, and react for 25 minutes. Then add 425 g of isoprene, control the maximum temperature to be less than 105 ° C, and react for 25 minutes. Finally, add 0.8 mmol of methyl benzoate, 0.7 mmol of ethyl benzoate and 0.8 mmol of ethyl acetate at the same time, and react for 25 minutes. Discharge, add antioxidant BHT 2.0 g and TNP 2.5 g, stir evenly, and after the product is condensed and dried, the SI content is tested to be 10.0%.

[0029] SIS was subjected to heating test: at 100℃, 0.5h, the SI content was 10.0%; at 130℃, 0.5h, the SI content was 14.0%; at 150℃, 0.5h, the SI content was 28.0%; at 180℃, 0.5h, the SI content was 41.0%; at 200℃, 0.5h, the SI content was 50.0%.

[0030] Comparative Example 1: Add 2.5 kg of cyclohexane, 75 g of styrene and 0.3 g of tetrahydrofuran to a 5 L reactor, add 5 mmol of initiator n-butyl lithium at 45-55 ° C, and react for 25 minutes. Then add 425 g of isoprene, control the maximum temperature to be less than 105 ° C, and react for 25 minutes. Finally, add 2.3 mmol of dichlorodimethylsilane and react for 25 minutes. Discharge, add antioxidant BHT 2.0 g and TNP 2.5 g, stir evenly, and after condensation and drying, the SI content of the product is tested to be 10.0%.

[0031] SIS was subjected to heating tests: at 100°C, 0.5h, the SI content was 10.0%; at 130°C, 0.5h, the SI content was 11.0%; at 150°C, 0.5h, the SI content was 11.0%; at 180°C, 0.5h, the SI content was 11.0%; at 200°C, 0.5h, the SI content was 12.0%.

[0032] Comparative Example 2: Add 2.5 kg of cyclohexane, 75 g of styrene and 0.3 g of tetrahydrofuran to a 5 L reactor, add 5 mmol of initiator n-butyl lithium at 45-55 °C, and react for 25 min. Add 425 g of isoprene, control the maximum temperature to be less than 105 °C, and react for 25 min. Finally, add 1.6 mmol of dichlorodimethylsilane and react for 25 min. Discharge, add antioxidant BHT 2.0 g and TNP 2.5 g, stir evenly, and after condensation and drying, the SI content of the product is tested to be 40.0%.

[0033] The SIS was heated and tested: at 100℃, 0.5h, the SI content was 41.0%; at 130℃, 0.5h, the SI content was 41.0%; at 150℃, 0.5h, the SI content was 41.0%; at 180℃, 0.5h, the SI content was 42.0%; at 200℃, 0.5h, the SI content was 42.0%.

[0034] Comparative Example 3: Add 2.5 kg of cyclohexane, 75 g of styrene and 0.3 g of tetrahydrofuran to a 5 L reactor, add 5 mmol of initiator n-butyl lithium at 45-55 ° C, and react for 25 minutes. Then add 425 g of isoprene, control the maximum temperature to be less than 105 ° C, and react for 25 minutes. Finally, add 1.7 mmol of 1,2-dichloroethane and react for 25 minutes. Discharge, add antioxidant BHT 2.0 g and TNP 2.5 g, stir evenly, and after condensation and drying, the SI content of the product is tested to be 38.0%.

[0035] SIS was subjected to heating test: at 100℃, 0.5h, the SI content was 38.0%; at 130℃, 0.5h, the SI content was 38.0%; at 150℃, 0.5h, the SI content was 40.0%; at 180℃, 0.5h, the SI content was 40.0%; at 200℃, 0.5h, the SI content was 41.0%.

[0036] By comparing and analyzing the above-mentioned embodiments and comparative examples: conventional coupling agents such as dichlorodimethylsilane, 1,2-dichloroethane, etc., have high coupling bond energy, and the coupling bond is almost not broken under the downstream use temperature conditions (about 100°C-200°C), which is manifested as the SI content of the elastomer product being almost unchanged under the downstream use temperature conditions (about 100°C-200°C). However, when the coupling agent of the present application is used, the ester bond plays a coupling role, the coupling bond energy is moderate, and the coupling bond is almost not broken under the synthesis temperature conditions (below 105°C). Under the downstream use temperature conditions (about 100°C-200°C), the downstream manufacturers can adjust the use temperature to control the breaking rate of the coupling bond and generate the required SI content to meet the downstream application requirements. In other words, the downstream manufacturers only need to reserve one elastomer product, and by adjusting the use temperature during application, they can obtain the elastomer with the required SI content, which can greatly save the material reserve cost, thereby reducing the production cost.

[0037] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a styrene-based thermoplastic elastomer, characterized in that: The following steps are involved: Step 1: Add styrene monomer, solvent cyclohexane and activator tetrahydrofuran into a reaction kettle, mix well and heat to 45°C to 55°C, add initiator n-butyl lithium, react under stirring for 20min to 30min; Step 2: adding isoprene monomer or butadiene monomer at a temperature of 55°C to 60°C, controlling the reaction temperature to be lower than 105°C, and reacting for 20min to 30min; Step 3, adding a coupling agent, and continuing the reaction for 5 to 25 minutes under stirring; discharging the material, and post-treating the glue to obtain a styrene-based thermoplastic elastomer product, wherein the coupling agent is one or a mixture of methyl benzoate, ethyl benzoate or ethyl acetate; The mass ratio of styrene monomer to isoprene monomer or butadiene monomer is 1:9 to 1:1; The molar ratio of coupling agent to initiator is 0.05~0.

5.

2. The method for preparing a styrene-based thermoplastic elastomer according to claim 1, characterized in that: The styrene monomer is styrene or α-methylstyrene.

3. The method for preparing a styrene-based thermoplastic elastomer according to claim 1 or 2, characterized in that: In the step three, after discharging, antioxidant BHT and antioxidant TNP are added to the glue solution, the amount of antioxidant BHT and antioxidant TNP is 0.3wt% to 0.6wt% of the total amount of styrene monomers, and the mixture is stirred evenly. The glue solution is condensed and dried to obtain a styrene thermoplastic elastomer product.

4. The method for preparing a styrene-based thermoplastic elastomer according to claim 3, characterized in that: The melt index of the styrene-based thermoplastic elastomer product is 0.1 to 30.

0.

5. The method for preparing a styrene-based thermoplastic elastomer according to claim 4, characterized in that: The molecular weight of the styrene-based thermoplastic elastomer product is 50,000 to 400,000.

6. The method for preparing a styrene-based thermoplastic elastomer according to claim 5, characterized in that: In step 3, after discharging, the solid content of the glue solution is 12wt% to 18wt%.